Joan Baez made a surprise appearance at San Francisco’s Castro Theatre, joining Indigo Girls during the encore its sold-out tour opener.

Baez, who has largely stepped away from touring in recent years, came onstage after singer-songwriter Matt Nathanson joined the Atlanta folk-rock duo, Amy Ray and Emily Saliers, for “Kid Fears” on Tuesday, May 12.

Before singing with Indigo Girls, Baez read a new poem, “Better Out Than In,” a raw spoken-word piece about rage, grief and release.

“How do you feel about being able to create a community right here?” Baez asked the crowd. “That’s the most important thing.”

Baez, long associated with Northern California’s folk and protest music history, then joined Indigo Girls for the Band’s “The Night They Drove Old Dixie Down.”

The moment came near the end of a 23-song set that drew from across Indigo Girls’ four-decade catalog. The setlist included “Least Complicated,” “Get Out the Map,” “Power of Two,” “Galileo” and “Closer to Fine,” which closed the show after the guest appearances.

The Castro Theatre date was the first of two sold-out San Francisco performances for Indigo Girls, who were scheduled to return to the venue Wednesday, May 13.

The concert also followed a recent public health disclosure from Saliers, who told fans before the tour that she has been diagnosed with cervical dystonia with torticollis and essential tremor, two incurable movement disorders that have affected her singing voice.

In an Instagram video with Ray, Saliers said the conditions cause involuntary muscle contractions in her neck as well as tremors in her jaw, throat and diaphragm, making it impossible for her to hold the long, straight tones that have been central to Indigo Girls’ harmonies.

Saliers noted she is working with specialists and using treatments including therapeutic massage, physical therapy, acupuncture and Botox shots, but acknowledged, “my voice will not be what it was.”

At the Castro, Saliers performed her solo song “Train Inside,” while Ray included her solo song “Tear It Down.” The two musicians has said they will keep touring while doing what they can to adapt their live sound, including adding other singers and using digital tools when needed.

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This article originally published at Joan Baez makes surprise appearance with Indigo Girls in San Francisco.